OBJECTIVES: The Behavior Core will provide a central source for the design, coordination, execution and interpretation of behavioral studies on mice generated in these projects. Behavioral phenotyping will involve a multi-level analysis. For newly generated lines this includes a general assessment of the overall health and functioning of the mice as well as evaluation of performance on a battery of behavioral protocols designed to characterize traits such as learning, motor coordination and anxiety. An additional series of behavioral protocols are proposed specifically targeted at hypotheses in the projects regarding responses to drug administration, such as tolerance and sensitization. Some mutant lines have already been characterized for their general behavioral phenotype, and for these lines testing will be more limited,directed specifically at hypothesis testing for the projects. FACILITIES: Adequate mouse housing and testing spaces have been guaranteed by the Dean of the Medical School. The behavioral Core personnel would maintain the equipment, supervise the training of investigators, facilitate communication between Center personnel and External Advisors, and perform generalized behavioral assessments of the mice generated within the Center.